The present invention relates to vapor deposited substantially transparent free standing polycrystalline diamond films. More particularly, the present invention relates to substantially transparent diamond films having a thickness of at least 50 microns and a measurable light transmittance which is thickness dependent.
As taught by Spear, Diamond-Ceramic Coating of the Future, Journal of American Ceramics Society, 72[2]171-91 (1989), the growth of single-crystal films of diamond is critical to many electronic and optical applications, but it is a feat that has not been achieved except for homoepitaxial growth on diamond substrates. There is reported by Peter K. Backmann, et al in the May 15, 1989, edition of Chemical and Engineering News, on page 38, that vapor deposited diamond heat sinks have been developed using plasma jet deposition to produce polycrystalline material up to 4.times.6.times.1 millimeter.
In Japanese patent 85,141,697, it is reported that free-standing diamond films have been found useful as diaphragms for speakers. S. Kawachi et al, Japanese patent 85(60)-127,292, reports that 10 micron diamond films have been deposited on a graphite substrate. K. Fujii, et al, Japanese patent 85(60)-186,500 teaches that a 6.5 micron thick transparent film can be produced on a substrate using a methane-hydrogen mixture.
Although various procedures have been developed to make vapor deposited polycrystalline diamond film, it would be desirable to provide glazing materials and heat sinks in the form of free-standing polycrystalline transparent diamond films having thicknesses of from 50 to 5000 microns with lateral dimensions exceeding 10 millimeters. As used hereinafter, the term substantially transparent is also intended to include translucent which means a material which is capable of transmitting light.